One nitrogen atom, three hydrogen atoms. That’s all it takes to make the basic ammonia molecule. This simple compound was one of the most important building blocks for the origin of life, scientists believe, providing the nitrogen that is crucial to many organic compounds. They just don’t know for sure how so much of it could form under the conditions of the early Earth.
In a new study this week, Sandra Pizzarello and colleagues tie the ammonia surplus to one of the more fascinating theories about the rise of life—that some of its basic components seeded the Earth from space on board meteorites that pounded the planet’s surface.
Pizzarello’s team analyzed a particular meteorite found in Antarctica. Its name is Graves Nunataks (GRA) 95229, and it was discovered in 1995. But its important characteristic is that the it belongs to a class of meteorites called carbonaceous chondrites that are full of organic materials. In the lab, the researchers tried to simulate how those materials in GRA 95299 might have reacted when they reached the younger Earth.
Pizzarello and her co-authors subjected a sample of the meteorite … to temperatures of 300 degrees Celsius at high pressures in the presence of water to simulate hydrothermal conditions on the meteorite’s parent asteroid or on Earth. Under heat and pressure, GRA 95229 released almost nothing but ammonia, in amounts that constitute roughly 1 percent by mass of the type of meteoritic material examined. Its parent asteroid, the authors speculate, must have been rich in ammonia. [Scientific American]
Four decades later, the Murchison meteorite is still full of surprises. When this extraterrestrial hunk fell to Earth near its namesake town in Australia in 1969, people managed to salvage more than 200 pounds of it. And now a new analysis of the meteorite, published this week in the Proceedings of the National Academy of Sciences, shows that it could hold millions of carbon-containing compounds. Researchers say the findings provide insight into the complex chemistry present when the chunk of space-rock formed, back when our solar system was young.
Back in 1969, researchers found amino acids and many other molecules in the carbon-rich rock. Many researchers have analyzed the chondritic meteorite for amino acids and other possible precursors to life, because some theories hold that life on Earth began with the delivery of prebiotic organic compounds from space via asteroids or comets [Scientific American]. But scanning techniques have advanced since then, so the new team used tools like ultra-high-resolution mass spectrometry to take a fresh look at the meteorite.
They saw it coming, and they got what was coming to them. For the first time, researchers not only detected an asteroid in space, but also tracked its progress and then collected its debris after it crashed to Earth [Science News].
Astronomers won the space lottery last October when they spotted a small, car-sized asteroid headed straight for Earth 19 hours before it reached our planet, and were able to study it as it plunged towards the atmosphere. When the rock exploded about 23 miles above the Nubian Desert in northern Sudan, many astronomers thought that was the end of an already remarkable story. But researcher Peter Jenniskens decided to see if any fragments had reached the Earth’s surface, and joined forces with a team of Sudanese scientists and students to comb the desert.
Small asteroids like 2008 TC3 are fairly common, with about one asteroid impacting Earth each year. But these small asteroids are usually not spotted until they enter the Earth’s atmosphere. “It’s like when bugs splatter on the windshield. You don’t see the bug until it’s too late,” says physicist and study coauthor Mark Boslough [Science News]. Researchers got lucky with this asteroid–it was spotted by chance by an observatory in Arizona.